The Genetics Core will provide two major services: 1) Transgenic and knockout mouse production and 2) Speed congenics. The transgenic and knockout mouse production facility will build on an existing facility that currently serves the Department of Pathology and Immunology. A particularly skilled technical staff is capable of microinjection of the pronuclei of fertilized ova and blastocysts. The current application proposes to add another microinjectionist who will permit the facility to provide additional services including blastocyst complementation, derivation of new embryonic stem cell lines, cryopreservation, and mouse embryonic fibroblast production. The speed congenics facility will be newly established and will provide genome wide typing for the purposes of enhancing backcrossing of mice into defined genetic backgrounds. The facility will be especially capable of helping the backcrossing of mice into rheumatic disease susceptible mouse models.